Processing of a large variety of consumer and industrial products, such as food, plastic, pharmaceutical and chemical products, usually involves one or more mixing steps for mixing the component materials of the products. Such mixing steps are oftentimes accompanied by simultaneous drying of the material being mixed and granulation of the material.
For accomplishing such mixing, large-capacity industrial mixers are utilized which are able to handle very large loads of material for more efficient and cost-effective mixing. One type of mixer design, which is able to effectively mix large loads of material, is referred to as a horizontal mixer because its elongated mixing chamber is disposed generally horizontally with respect to the ground surface on which it rests. More specifically, horizontal mixers generally comprise a mixing chamber, an elongated, horizontal mixing shaft which rotates, and a plurality of mixing tools, such as mixing plows, which extend generally perpendicularly from the horizontal shaft to rotate around the inside of the chamber. The mixing plows are configured and dimensioned as required for the mixing process to follow the cylindrical inside walls of the chamber for proper mixing of all of the material in the chamber when the mixing shaft rotates.
Supplementing the mixing action within the chamber that is provided by the plows, are chopper assemblies which include chopper blades. The chopper assemblies operate in conjunction with the mixing plows to enhance the mixing process. The chopper blades of the assemblies are positioned to rotate and thereby chop material within the mixing chamber. To that end, the blades are coupled to chopper shafts linked to a motor, which is generally mounted outside of the chamber. Usually a plurality of chopper assemblies are utilized with the mixer, each assembly being powered independently from the other by a separate shaft and motor. The assemblies are operable for rotating the blades in the range of approximately 3000-3600 RPM, for example, and are used for a variety of purposes within the mixing process. Each assembly will usually include multiple, staggered blades on a shaft for more intense action.
For example, chopper blades are used to quickly mix and disperse minor ingredients within a mixed solution. The chopper blades also are used to introduce high impact and shear to a material mixture, such as to introduce heat into the mixture. Still further, the chopper blades are utilized for other process steps, such as dispensing fluids through a mixed solution, reduction of the size of particles formed within the material mixture, and the break up of agglomerates within the mixed material (i.e., deagglomeration).
Typical chopper blades in available mixers are made of stainless steel. Due to their high rotational speeds and the high impact and shear the blades introduce to a material mixture, chopper blades are subject to a significant amount of wear during a mixing process. Such wear eventually limits the useful life of the blades. For example, FIG. 2A illustrates a typical chopper blade 2 formed of stainless steel and having cutting edges 4, 5 and an aperture 6 for mounting the blade to a chopper shaft for rotation. FIG. 2B illustrates the same blade after it has been used within a mixer for a certain amount of time. The cutting edges 4, 5 are significantly worn, as may be seen in the figure. As a result, blade 2 must be periodically replaced in the mixer. Such constant replacement increases the cost of maintenance and operation of the mixer. Not only do new chopper blades have to be purchased, but the mixer itself has to be shut down for the necessary blade replacements and maintenance. This amounts to a significant cost. As many as eight blades per assembly, and four or more assemblies per mixer (32 blades) may need to be maintained and replaced. Furthermore, the shutdown decreases the overall efficiency of the mixer and the mixing process.
Wear of the blades also may present a possibility of product contamination. The particles from the worn blades mix with the product in the mixer.
Certain attempts have been made to increase the useful life of chopper blades used in mixers. For example, abrasion resistant coatings are often applied to blades to increase their effective life. Furthermore, different materials for formulating the blades have been tried. However, despite these various efforts, there is still a need in the art for improvements to mixers using chopper assemblies with chopper blades to increase the effective life of the blades, increase the overall efficiency of the mixing process, and thereby reduce the costs of operating and maintaining a mixer.
Therefore, it is an objective of the invention to improve material mixers and to increase their operational life span between maintenance shutdowns.
It is another objective to improve material mixers by increasing the effective operational life of chopper blades used in such mixers.
It is still another objective of the invention to increase the efficiency of an industrial mixing process and to reduce the operational and maintenance costs of a mixing process.
It is another objective to minimize product contamination by reducing blade wear.
These objectives and other objectives are addressed by the invention as set forth below in the description of the invention.